It is known to join a number of triangular frame elements at their vertices to construct a truss structure having the shape of an oblique trianglar prism. The integrity of the completed truss structure depends in part on the dimensions of the individual frame elements and their alignment. The latter factors are in turn governed by the precision and alignment of the vertex fittings. Thus, accurate alignment of surfaces, slots and holes in the three types of vertex fittings used to construct a frame element is required. The critical centering and mating of holes, slots and surfaces of the individual vertex fittings with the struts used in the truss structure is difficult and expensive to achieve when each fitting is machined separately. Unless achieved, it may lead to misalignment in the construction of the individual frame elements or of the truss structure, to increased costs and time of construction, and to waste of materials and parts.